This project proposes the development of a new imaging technique for improving the performance of medical ultrasound imaging systems when used with microbubble-based contrast agents The ultimate goal is the provision of a system for excitation enhanced ultrasound contrast imaging with a higher sensitivity than current ultrasound scanners. The new ultrasound system will utilize two acoustic fields: one for microbubble excitation and one for imaging. The excitation field will momentarily increase the number of bubbles with an instantaneous size close to the resonance size corresponding to the imaging field. If the imaging field is applied simultaneously with or slightly after the excitation field, acoustic scattering from the excited bubbles will become markedly stronger (at least 6 dB) than without the excitation field. An experimental, in vitro system will be constructed for activating the growth of the contrast microbubbles and for measuring the corresponding shifts in the microbubble size- distribution and the changes in fundamental and second harmonic backscattering Experimental conditions will be established for optimizing scattered signals from contrast agents to improve the signal-to-noise ratio in both conventional and harmonic imaging modalities. Excitation enhanced ultrasound contrast imaging will enable clinicians to better depict contrast containing tissues and, thus, better diagnose vascular abnormalities including tumors. PROPOSED COMMERCIAL APPLICATIONS: Ultrasonic Imaging is now the second most widely used imaging modality after x-ray. Its usage has increased in recent years due to the development of ultrasound specific contrast agents. The proposed research will accelerate the usefulness of contrast agents for many significant clinical applications.